Biodiversity hidden to the naked eye

Microorganisms are incredibly diverse. A small sample of water from a local pond can contain dozens of species - some related to plants, some related to fungi, and some belonging to completely different, ancient lineages of eukaryotes (see simplified eukaryotic tree of life above). Algae are a subset of this diversity: they are organisms that contain a photosynthetic organelle (plastid). Here are a few examples of the charismatic algae found in the vicinity of the University of Connecticut. Click here to see the map of localities sampled so far
Current total: 150 species!

Many microscopic and macroscopic algae belong to the group called Stramenopiles (also referred to as heterokonts). Diatoms, Chrysophytes, and Synurophytes are microscopic, and Phaeophytes (kelps, or brown algae) are mostly macroscopic and marine.

Chrysophytes and Synurophytes

Dinobryon is a colonial flagellated alga from the class Chrysophyceae. Another colonial chrysophyte is Uroglenopsis, also found in CT.

Synura is a genus of the Synurophyceae, the sister group of Chrysophyceae. Their plastids give members of both groups a typical golden-brown color. Synurophyceae have cells covered with siliceous scales and detailed examination of scale morphology is often needed for species identification. Colonies of Synura are not the most elegant of swimmers, but are fun to watch tumbling around.

Mallomonas is a common solitary synurophyte. Its cells are also covered in scales and often equipped with long bristles attached to the scales. Note how large the cell is in comparison to the individual cells in the colony of Synura.

Diatoms

Diatoms (Bacillariophyceae) are very common not only in freshwater habitats, but also in marine environments. They can be solitary cells or form chains or stalked colonies. Their cells are enclosed in siliceous cases called frustules, which bear fine ornamentation best visible under high magnifications or under a scanning microscope. These fine structures of the frustules are used to identify diatom species.

Raphidophytes

Gonyostomum is one of the few members of the small phylum Raphidophyta. It can form nuisance blooms.

Gonyostomum semen from a wetland at Bigelow Hollow, Union, CT

Cryptophytes

Cryptophyta is an ancient lineage of photosynthetic eukaryotes. One of the few common species is the flagellate Cryptomonas, which can be found in most water bodies in CT.

Cryptomonas sp. from a tank in the EEB greenhouse, Storrs, CT

Dinoflagellates

Dinoflagellates are members of the Alveolata, a group related to the Stramenopiles. Ceratium and Peridinium are common freshwater genera.

Ceratium hirundinella from Middle Bolton Lake, Vernon, CT

Peridinium cf. cinctum from Breakneck Pond, Union, CT

Parvodinium umbonatum from Breakneck Pond, Union, CT

Gymnodinium sp. from wetland on Mansfield City Rd., Eagleville, CT

Cyanobacteria

Some "algae" are not even eukaryotic - the photosynthetic Cyanobacteria (some of which gave rise to chloroplasts) are sometimes also referred to as "blue-green algae". They are morphologically diverse, ranging from unicellular to colonial to filamentous. They are very common and in some cases even form toxic blooms.

Rhodophyta

Rhodophyta, or red algae, are common in marine habitats and are especially diverse in the tropics. Several of these macroscopic seaweeds are used for human consumption, e.g., Porphyra or nori is used for sushi wraps. There are freshwater rhodophytes, though, both microscopic and macroscopic. The branched filaments of Batrachospermum and Tuomeya are often found in small streams, while the unbranched, stiff and knobby filaments of Lemanea typically grow in tufts around dams. These algae are macroscopic but hard to find if you don't know what you are looking for. All three genera occur in Connecticut.

Lemanea sp. from Eagleville Dam, Eagleville, CT

close-up of a dissected filament of Lemanea sp. from Eagleville Dam, Eagleville, CT

Euglenoids

Euglenoids are an ancient lineage most closely related to Kinetoplastida (best known for the parasite Trypanosoma). They acquired photosynthetic abilities by engulfing a green alga - and therefore they may superficially resemble one. Among the commonly occurring genera are Euglena, Trachelomonas, and Phacus.

Unlike green algae, which store energy in form of starch, euglenoids use a different carbohydrate, paramylon. The paramylon bodies are often large and of a white-ish, "shiny" appearance, like the one visible in the Phacus specimen below.

Phacus orbicularis from pond on Forest Rd., Mansfield, CT

Phacus longicaudatus from River Park, Tolland, CT

Phacus tortus from wetland on Mansfield City Rd., Eagleville, CT

Euglena sp. from Breakneck Pond, Union, CT; video of another Euglena species from Tift Pond here

Green algae: Chlorophyta

Some algae grow on plants or on other algae - epiphytically. Aphanochaete from the order Chaetophorales, is an example of a green filamentous alga growing on another green filamentous alga, Oedogonium (order Oedogoniales).

Other free-living filamentous algae are Microspora, the branching Chaetophora, the above mentioned Oedogonium, and Bulbochaete - a relative of Oedogonium with branched filaments ending in long projections.

Green algae often produce swimming cells as part of their life cycles. As an example, a video of a swimming cell of Oedogoniumcan be found here.

Dictyosphaerium pulchellum, a colonial alga from wetland on Mansfield City Rd., Eagleville, CT

Tetraedron regulare from wetland on Mansfield City Rd., Eagleville, CT

Tetraedron enorme from wetland on Mansfield City Rd., Eagleville, CT

Some green algae form colonies with defined numbers of cells (4, 8, 16, etc.). Such colonies are called coenobia. Commonly found coenobial green algae are Pediastrum, Stauridium, Coelastrum, Desmodesmus, and Scenedesmus from the order Sphaeropleales. Their sister order Volvocales also contains several coenobial representatives, for example: Eudorina, Pleodorina, Pandorina, and Volvox.

Green algae: Streptophyta

Conjugating green algae (Zygnemophyceae)

Desmidiales

The order Desmidiales contains some of the most spectacular of algae. Many species of the crescent-shaped Closterium can be found in the Northeast, as well as Cosmarium, Staurastrum, Euastrum, Micrasterias, Xanthidium, and others.

other Streptophyte classes

Klebsormidiales are a group of inconspicuous but commonly occurring filamentous algae.

Coleochaetales are among the closest relatives of land plants. Some species retain and nourish the fertilized zygote (this is called matritrophy) and form disc-like thalli (bodies) that often grow attached to aquatic plants or other substrates.

Klebsormidium sp. from Halls Pond, Chaplin, CT

Coleochaete scutata from Bigelow Pond, Union, CT

Not all algae are microscopic. Aside from the conspicuous marine seaweeds, several freshwater algae are also observable by the naked eye. The green algae of the class Charophyceae (stoneworts) can be found in many water bodies in the Northeast, but can be easily mistaken for aquatic plants.

Nitella flexilis from Walker Reservoir East, Vernon, CT

Chara zeylanica from the EEB greenhouse, Storrs, CT, and a closeup of its reproductive structure (oospore)

And let's not forget the most famous lineage of Streptophyta - land plants!